Made libc debug symbols get copied to image when building a dev image.
Made libc debug symbols get copied to image when building a dev image.

libc debug symbols (libpthread in particular) are needed to debug threaded software with gdb. This CL copies
debug symbols for glibc when building a dev image.

This CL also removes an old hack related to selecting the correct path to the glibc tarball.

BUG=chromium-os:16847
TEST=Build dev image (--withdev is the default). Checked that debug info is copied. Booted image and checked
the debugging threaded programs works with gdb. Build non-dev image (--nowithdev) checked that debug info is
not copied.

Change-Id: Id908e8260b1431ed1256a13dfb86b05ac242f263
Reviewed-on: http://gerrit.chromium.org/gerrit/3091
Reviewed-by: Chris Sosa <959d3d631fb6f17f1b07f751372041a1edb210d1@chromium.org>
Tested-by: Raymes Khoury <348ad72dc039a127ca70ef38e5de4eebe052b884@chromium.org>

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